Hydraulic Hammer

ABSTRACT

A piston cylinder is formed inside a ram and is fitted with a piston attached to a stationary hollow piston rod, creating a upper piston chamber for receiving pressurized hydraulic fluid, which causes the ram to rise as the volume of the upper piston chamber is expanded due to the hydraulic pressure and increasing volume of hydraulic fluid. When the ram reaches predetermined desired height, hydraulic pressure is released by opening a directional valve, allowing the ram to drop. A lower piston chamber is sealed and filled with gas. A moveable shuttle member that reciprocates up and down inside a hollow piston rod in response to the changing volume of the lower piston cylinder, facilitating the evacuation of hydraulic fluid from the upper piston chamber. An alternative embodiment uses a single fluid and has no shuttle member.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

SEQUENCE LISTING

Not applicable

BACKGROUND OF THE INVENTION

The present invention is related to an improved hydraulic hammerprincipally for driving piles into the earth.

DESCRIPTION OF THE RELATED ART INCLUDING INFORMATION DISCLOSED UNDER 37C.F.R. 1.97 AND 1.98

Many structures, including for example, buildings, piers and the like,are supported by piles that are driven into the ground, either dryground or ground that is underwater.

Dropping a free weight of a certain weight from a certain height is onecommon technique for driving piles. An advantage of this technique isthat the force needed to drive the pile further corresponds to the loadthe pile can bear in use and well-known tables allow builder tocalculate the load bearing capacity very accurately. A disadvantage ofthis technique is that the weight must be raised a substantial heightand the lifting mechanism, typically a crane, is even higher, requiringa good deal of space, or headroom, available above the pile. Anotherdisadvantage of this technique is that it is typically relatively slow,reducing productivity.

Also frequently used for driving piles are hydraulic hammers. Onehydraulic hammer is disclosed in U.S. Pat. No. 6,557,647, whichdescribes a hammer having a piston cylinder inside a ram, with thestationary piston fixed to a stationary solid piston rod, which is fixedto the bottom of the ram. The piston forms an upper piston cylinderabove the piston and a lower piston cylinder below the piston. Hydraulicfluid under pressure is forced into a lower piston chamber to raise theram above the pile and hydraulic fluid under pressure is forced into theupper chamber as the ram fall toward the extended, or striking,position. A substantial physical portion of this device lies outside ofthe ram, increasing the headroom needed for its operation. The structureis also mechanically complex. It also requires several valves.

Therefore, there is a need for a low headroom hammer that is a hydraulichammer.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to providea nearly free-fall hydraulic hammer that has a faster cycle time thanconventional hammers and, in some embodiments, to provide a low-headroomhydraulic hammer.

It is another object of the present invention to provide a hydraulichammer that requires less energy to operate than similar conventionalhammers.

It is another object of the present invention to provide a nearlyfree-fall low headroom hydraulic hammer that has a smaller overallweight than comparable hammers of similar impact.

It is another object of the present invention to provide a nearlyfree-fall low headroom hydraulic hammer that has a low headroom,permitting its use in situations where a hammer cannot be raised highabove the pile to be driven, i.e., a low headroom environment.

It is another object of the present invention to provide a nearlyfree-fall low headroom hydraulic hammer that mimics the impact force ofa true free-falling hammer or weight, which have very precise drivingproperty tables for calculating pile load bearing factors, allowing thepresent hammer to utilize these well-developed load tables.

These and other objects of the invention are achieved by providing anearly free-fall hydraulic hammer, which may be a low-headroom hydraulichammer, in which a ram having a piston cylinder inside it is lifted bypumping hydraulic fluid into the chamber above a stationary piston andthen dropping the ram by relieving the pressure on the hydraulic fluid.The low-headroom hydraulic hammer is made a relatively short andtherefore, low headroom, hammer by having the cylinder and the pistonlocated entirely inside the ram or actuator. A closed sealed compressedgas chamber in the piston cylinder below the piston and continuing upinto a hollow piston rod provides a spring-like bounce to accelerate theoutflow of the hydraulic fluid from the chamber above the piston. In oneembodiment a sealed cylindrical shuttle member inside the hollow pistonconnecting rod reciprocates between an upper stop member and a lowerstop member, to change the gas pressure inside the sealed gas chamberand also serves as a barrier between the hydraulic fluid and the gas,keeping them separated. In another embodiment, the shuttle member isomitted and only a single working fluid, a hydraulic fluid is used. Inanother embodiment a receptacle, resembling a bucket or other convenientshape, is connected to the bottom of the piston to old hydraulic fluidand thereby reduce the volume of hydraulic fluid that must be pumped,thereby reducing the cycling time for a give size hydraulic pump andincreasing the efficiency of the hydraulic hammer. In all embodiments,the ram of the hammer moves between a first position, which is the ramat its maximum lift point above the pile, which is predetermined, and asecond position, which is the lowest position of the ram, i.e., thestriking position.

Other objects and advantages of the present invention will becomeapparent from the following description taken in connection with theaccompanying drawings, wherein is set forth by way of illustration andexample, the preferred embodiment of the present invention and the bestmode currently known to the inventor for carrying out the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross section side view of a first embodiment of a hydraulichammer (hammer) according to the present invention having areciprocating shuttle member inside a hollow piston rod and showing thehammer at the completion of a downward strike on a pile or the like inequilibrium, at rest and ready to begin the lifting stroke of its cycle,that is, in a second position.

FIG. 2 is a cross section side view of the hammer of FIG. 1 at thebeginning the hammer lifting stroke.

FIG. 3 is a cross section side view of the hammer of FIG. 1 shown at aposition during the lifting stroke of the ram.

FIG. 4 is a cross section side view of the hammer of FIG. 1 shown at thetop of its predetermined height and the beginning of the falling strokeof the ram, that is, in a first position.

FIG. 5 is a cross section side view of the hammer of FIG. 1 shown duringthe falling stroke of the ram.

FIG. 6 is a cross section side view of the hammer of FIG. 1 shown at theend of the falling stroke, having made impact with the pile or otherdriven object, at which point, the hammer is returned to theconfiguration of FIG. 1, in equilibrium, at rest and ready to beginanother cycle.

FIG. 7 is a cross section taken along lines 7-7 of FIG. 1 or FIG. 8.

FIG. 8 is a cross section side view of another embodiment of a hydraulichammer (hammer) according to the present invention showing the hammer atthe completion of a downward strike on a pile or the like inequilibrium, at rest and ready to begin the lifting stroke of its cycle.

FIG. 9 is a cross section side view of the hammer of FIG. 8 at thebeginning the hammer lifting stroke.

FIG. 10 is a cross section side view of the hammer of FIG. 8 shown at aposition during the lifting stroke of the ram.

FIG. 11 is a cross section side view of the hammer of FIG. 8 shown atthe top of its predetermined height and the beginning of the fallingstroke of the ram.

FIG. 12 is a cross section side view of the hammer of FIG. 8 shownduring the falling stroke of the ram.

FIG. 13 is a cross section side view of the hammer of FIG. 8 shown atthe end of the falling stroke, having made impact with the pile or otherdriven object, at which point, the hammer is returned to theconfiguration of FIG. 8, in equilibrium, at rest and ready to beginanother cycle.

FIG. 14 is a cross section side view of another embodiment hydraulichammer, in which a cylinder having a closed lower end is attached to thelower surface of a piston, i.e., forming a receptacle resembling abucket, suspended beneath the piston and reciprocating within a wellbelow the otherwise normal floor of the piston cylinder to reduce thevolume of fluid that must be removed from the cylinder space below thepiston, according to the present invention showing the hammer at thecompletion of a downward strike on a pile or the like in equilibrium, atrest and ready to begin the lifting stroke of its cycle.

FIG. 15 is a cross section side view of the hammer of FIG. 14 at thebeginning the hammer lifting stroke.

FIG. 16 is a cross section side view of the hammer of FIG. 14 shown at aposition during the lifting stroke of the ram.

FIG. 17 is a cross section side view of the hammer of FIG. 14 shown atthe top of its predetermined height and the beginning of the fallingstroke of the ram.

FIG. 18 is a cross section side view of the hammer of FIG. 14 shownduring the falling stroke of the ram.

FIG. 19 is a cross section side view of the hammer of FIG. 14 shown atthe end of the falling stroke, having made impact with the pile or otherdriven object, at which point, the hammer is returned to theconfiguration of FIG. 8, in equilibrium, at rest and ready to beginanother cycle.

FIG. 20 is a cross section side view of another embodiment hydraulichammer of FIG. 14, in which a lid seals the receptacle attached beneaththe piston reciprocates within a well below the otherwise normal floorof the piston cylinder to reduce the weight of fluid that reciprocates,showing the hammer at the completion of a downward strike on a pile orthe like in equilibrium, at rest and ready to begin the lifting strokeof its cycle.

FIG. 21 is a cross section side view of FIG. 14 showing an alternativeembodiment of the hydraulic hammer of FIG. 1 or FIG. 14 in which acylinder sleeve 17 forming a piston cylinder is only loosely seated in abore in the ram and the space between these elements is filled with afluid such as oil a first embodiment of a hydraulic hammer (hammer)according to the present invention having a reciprocating shuttle memberinside a hollow piston rod and showing the hammer at the completion of adownward strike on a pile or the like in equilibrium, at rest and readyto begin the lifting stroke of its cycle.

FIG. 22 is a cross section side view of an alternative embodiment of thehammer having a reciprocating shuttle member inside a hollow piston rodas shown in FIG. 1 and the reciprocating receptacle resembling a bucketsuspended below the piston and reciprocating with in a well below theotherwise normal floor of the piston cylinder as shown in FIG. 14,showing the hammer at the completion of a downward strike on a pile orthe like in equilibrium, at rest and ready to begin the lifting strokeof its cycle.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a hydraulic hammer 10 (“hammer” 10), in anembodiment illustrated in FIGS. 1-7 which is a low headroom hammer, ismounted on a frame or saddle 12, which is preferably a spherical bearingconnection and manifold, resting on a suitable supporting surface frame15 above the pile 14 that is to be driven, or other suitable object tobe driven, as the case may be. A hallmark of the hammer 10 is that thepiston cylinder 24 is formed wholly inside the ram 16, with only acylinder head 48 projecting above the top surface of the ram 16, whichallows the hammer 10 to be a low-headroom hammer for any given capacityof the hammer 10. The hammer 10 includes an “outer casing of theactuator” 16, that is a ram 16, which may be cylindrical or otherdesired cross section shape and that may include an inwardly taperedreduced neck portion 18, terminating in a reduced size impact or bottomportion 20 having a face 22 for striking the top surface of the pile 14.The face 22 may be flat, or have a convex dished shape. The hammer 10may employ a conventional external frame (not shown), which is connectedto the support frame 15 and which is principally cylindrical andencloses the vertical portion of the hydraulic hammer 10, with suitableguide rails to insure that the ram portion falls and rises along adesired straight path and may also include a suitable striker member(not shown) interposed between the ram 16 and the pile 13 to cushion theblow and prevent damage to the top of the pile 13.

Still referring to FIG. 1, the ram 16 is shown in a second position,that is, a striking position and is show FIG. 1 at the end of thestriking position, that is, without significant pressure in the hammer10. A piston cylinder 24, having a bottom wall 25 connected to acylindrical side wall 27, is formed inside the ram 16. The top of thepiston cylinder 24 is sealed by a cylinder head 48. The piston cylinder24 may be formed integrally into the ram 16 or preferably consists of asleeve 17 having a connected bottom wall 25 that is inserted into acavity 19 in the ram 16 to form the piston cylinder 24 and may be sealedby press-fitting or the like, permitting the use of a sleeve 17 andconnected bottom wall 25 of a different material that the ram 16 forlonger life, more accurate machining, replacement and the like. In analternative embodiment discussed in detail below, the sleeve 17 andconnected bottom wall 25 assembly is suspended within the cavity 19 inthe ram 16 with an annular space between these two members, which may bepartially filled with oil or other fluid. The piston cylinder 24 is adouble-acting cylinder with an accumulator. Enclosed within the pistoncylinder 24 is a piston 26 that is connected to a lower end 38 of ahollow piston rod cavity 28. The upper end 23 of the hollow piston rod,which is preferably tubular, is fixed to an upper portion of the frame12, so that the hollow piston rod 28 does not reciprocate. The piston 26is sealed against the piston cylinder 24 by suitable piston ring sealsto prevent the flow of fluids around the circumference of the piston 26,i.e. to prevent bypass or blow-by of fluids. Inside the hollow pistonrod 28 is a freely moving shuttle member 30 that reciprocates inresponse to changes in gas pressure below it and liquid fluid pressureabove it, with freedom to move constrained only the friction of itsseals against the hollow piston rod 28. The shuttle member 30 is a smallsolid cylindrical member that is preferably made of steel, brass or thelike and, in a typically sized hammer, is about 15 cm (6 in.) long andabout 5.5-7.75 cm (2.5-3 in.) in diameter and weighs about 14-16kilograms (30-35 pounds), depending on the size of a particular hammer10 and its desired stroke length, etc. The shuttle member 30 fits intothe longitudinal cylindrical cavity of the hollow piston rod 28, i.e.,the cavity 40 (see especially FIG. 7). The shuttle member 30, whichoperates as a hydraulic accumulator, i.e., to store energy and reducesystem shock, is fitted with appropriate seals to block the flow offluids past it in either direction. The shuttle member 30 is free tofloat between an upper stop member 32 that is adjacent to the top end 34of the piston rod 28 and a lower stop member 36, located adjacent to thelower end 38 of the piston rod 28. The upper stop member 32 and thelower stop member are preferably rings set into mating grooves in theinner surface of the hollow piston rod 28 and serve to constrain thereciprocal movements of the shuttle member 30. In FIG. 1, the shuttlemember 30 is shown in its highest position, creating the lowest gaspressure of the cycle of lifting and falling and at its lowest positionin FIG. 6, creating the highest gas pressure of the cycle of lifting andfalling.

Still referring to FIG. 1, the piston 26 is fixed to the lower end 38 ofthe piston rod 28 and these members are always stationary. It is the ram16 that moves up to a first or raised position (shown at its maximumheight in FIG. 4) and down relative to the piston 26 and piston rod 28,that is down to its second or lowest or striking position in which theram 16 strikes the top of the pile 14 (as first shown in FIG. 1). Thecylinder reciprocates up and down relative to the piston 26. The pistoncylinder 24 and the ram 16 that encloses and carries the piston cylinder24 reciprocates by sliding up or down along the piston 26. This is theopposite of an ordinary internal combustion engine or a pump in whichthe engine block is stationary and the piston reciprocates inside astationary cylinder and it is opposite of every existing hydraulic ramknown the inventors of the present invention. Also opposite is that thepiston rod 28 is stationary and that it does not transfer any power toanother part such as a crankshaft. Conceptually, the piston cylinder 24is the ram 16, or the piston cylinder 24 is formed in the ram 16 itself,however one wishes to view the structure. In either way of visualizingthe structure of the hammer 10, the piston cylinder 24 reciprocatesalong a stationary piston 26. The length of the lift and subsequent fallof the ram, i.e., its stroke, is about 1.1 meters (4 feet), but it canbe designed to longer or shorter, as desired.

Still referring to FIG. 1, the hammer 10 includes two separate fluidchambers for permitting fluid flows that raise and lower the ram 16. Theinterior volume 40 of the hollow piston rod 28 below the shuttle member30, and of the lower piston chamber 29, which is the volume of thepiston cylinder 24 above the bottom wall 25 of the piston cylinder 24and the lower surface 31 of the piston 26, both of which vary throughouta cycle, is filled with a substantially inert gas, preferably Nitrogen(to prevent Oxygen and oil from possibly forming an explosive mixtureand to prevent water formation) and operating at about 1,725 kPa (250psi) in a closed system in which the top end is defined by the shuttlemember 30, which is fitted with suitable seals to minimize leakage ofthe gas past it. This gas is indicated by the numeral 41, whichdesignates a variable volume cavity 41, and is shown by stippling, withthe volume of the varying volume cavity 41 varying during the cyclesshown by the stippled area in the drawings, i.e, the greatest volume isat the lowest point or striking point of the ram 16, e.g., FIG. 1, andthe smallest volume at the top of the stroke, or highest point of theram 16, e.g., FIG. 4, that is, when the piston 26 is closest to thebottom wall 26 of the piston cylinder. The variable volume 41 is formedby the lower piston chamber 29 and the hollow piston rod cavity 28 up tothe lower surface of said shuttle member 30, with the lower pistonchamber 29 and the said hollow piston rod cavity 28 being in fluidcommunication with each other.

These observations apply to all embodiments in this paper.Alternatively, in all embodiments, the working fluid may be water, whichmay be any water locally available, including salt water. The variablevolume of the lower piston chamber 29 and the cavity in the hollowpiston rod 28 up to the lower surface 66 of the shuttle member 30combine to form a single sealed chamber, whose volume changes as theposition of the ram 16 changes within the cylinder. Gas is added to thisclosed system only to maintain the desired pressure in the system. Theenclosed volume of the system increases and decreases as the shuttlemember 30 moves up and down inside the hollow piston rod 28 and as thelower piston chamber 29 moves up and down. The lower piston chamber 29and the portion of the cavity of the hollow piston rod 28 below a lowersurface 66 of said shuttle member 30 together form the sealed cavitythat is filled with a substantially inert gas under pressure, e.g.Nitrogen.

Still referring to FIG. 1, a hydraulic fluid conduit tube 42 isconcentric with and larger in diameter than the hollow piston rod 28, asbest seen in FIG. 7, and is larger in diameter than the hollow pistonrod 28 and is open to the top surface 44 of the piston 26 throughout thearea of the cross section of the hydraulic fluid conduit tube 42 that isoutside the cross section area of the hollow piston rod 28, that is, inthe tube passageway 46. The hollow piston rod 28, the hydraulic fluidconduit tube 42 and the variable cylinder volume above the top surface44 of the piston 28 are sealed by a top wall 48, that is, a cylinderhead 48. The passageway 46 opens into the larger diameter cylindervolume 50 above the top surface of the piston 28. The hydraulic fluidconduit tube 42 is connected to a high pressure line 52 that isconnected to a supply of hydraulic fluid pressurized by a high pressurepump 54. A pressure relief line 56 is connected to a pressure relieftank 58 at its distal end 60 and to the hollow piston rod 28 at itsproximal end 62. The shuttle member 30 seals the hydraulic fluid fromthe gas, with the hydraulic fluids always contained above the topsurface 64 of the shuttle member 30 and the gas always contained belowthe bottom surface 66 of the shuttle member 30. A directional valve 68allows (open) or disallows (closed) the flow of hydraulic fluid from thehigh pressure hydraulic fluid line 52 to the pressure relief line 56 andthereby controlling whether or not high pressure hydraulic fluid flowsinto the volume space 50 above the top surface 44 of the piston 26. Theflow of high-pressure hydraulic fluid into the upper piston chamber 50,exerting a downward force on the top surface 44 of the piston 28, and anupward force on the cylinder head 48. Since the piston cannot move, theincreasing volume of high pressure hydraulic fluid in the variable space50 requires that the cylinder head 48 and the attached ram 16 must belifted up.

Still referring to FIG. 1, the upper piston chamber 50, at its maximumvolume, is filled with hydraulic fluid, which may be any substantiallyincompressible fluid, such as petroleum oil or water, which requiresless fluid that comparable prior art hydraulic hammers of similar size,resulting in more efficient hydraulic hammers. The use of reducedvolumes of hydraulic fluid allows the use of a smaller capacity highpressure hydraulic fluid pump 54, reducing the energy needed to raisethe ram 16, and to faster cycle times, decreasing the time needed todrive a particular pile 14, both increasing the efficiency of theoverall pile driving operation.

As shown in FIG. 1, the directional valve 68 is open, so there is nopressure in the high pressure hydraulic line 52, the volume of thepiston cylinder chamber 50 above the piston 26 and below the cylinderhead 48 is at its minimum volume and the shuttle member 30 is at itshighest point, that is, pushing against the upper stop member 32, so thegas pressure in the lower piston chamber 29 is at its lowest while thelower piston chamber 29 is at the largest volume it will reach duringany portion of a cycle. The variable volume cavity 41, indicated bystippling in the relevant drawings, is at its maximum. In thisconfiguration, the ram 16 has just struck the pile 14 and the hammer 10is at rest and in equilibrium, ready to being the next cycle.

Referring to FIG. 2, the directional valve 68 closed, allowing thehydraulic pump 54 to pressurize the hydraulic fluid in the line 52,causing the hydraulic fluid to flow along the direction of the arrows 70and then into the passageway 46 of the hydraulic fluid conduit tube 42and then into the upper piston chamber 50, thereby exerting downwardforce on the top surface 44 of the piston 26. Since the cylinder head 48is stationary, the resulting forces on the hydraulic fluid and itsincreased volume force the ram 16 to move upward, lifting the face 22 ofthe ram 16 above the pile 14. At the same time, the gas in the lowerpiston chamber 29 and the interior of the hollow piston rod 28 is beingcompressed, as the volume of the lower piston chamber 29 decreases,forcing the shuttle member 30 to remain pressed against the upper stopmember 32. The volume of the upper piston chamber 50 and the volume ofthe lower piston chamber 29 change in inverse direct proportion to oneanother. This lifting step continues until the desired amount of lift isachieved, which may be any amount from zero, i.e., face 22 now beinglifted free from the top of the pile 14, up to the maximum lift strokeallowed by the design of a particular ram 16 of particular capacity andlift, but generally being a typical lift of about 3.5 meters (4 feet),which can be controlled by opening the directional valve 68 when thedesired about of lift has been achieved. This flexibility in operationallows the hammer 10 to be operated to produce any of a wide range offorces that might be desired on a particular job. Naturally, hammers 10of different sizes will have different, appropriate, maximum lifts.

Referring to FIGS. 3, 4 the lifting step of the process of FIG. 2, thatis, pumping high pressure hydraulic fluid into the passageway 46 of thehydraulic fluid conduit tube 42 and then into the upper piston chamber50, continues and the volume of the upper piston chamber 50 increases asthe volume of the hydraulic fluid in it increases and the volume of thelower piston chamber 29 continues to decrease, raising the ram 16progressively until the desired predetermined height is reached, asshown in FIG. 3.

Referring to FIG. 4, the desired predetermined height of the ram 16 hasbeen achieved and the ram 16 is now in a first position, and at thatpoint, the directional valve 68 is opened, providing an alternative andun-pressurized path for the hydraulic fluid flowing from the highpressure hydraulic pump 54 and for the pressurized hydraulic fluid inthe high pressure hydraulic fluid line 52, the hydraulic fluid conduittube 42 and the upper piston chamber 50. The variable volume cavity 41is here at its minimum volume and hence at its greatest pressure. Allthe hydraulic fluid in these cavities flows toward the pressure reliefline 56 and the connected pressure relief tank 58, immediately releasingall the pressure in these cavities, i.e., all the pressure and thevolume of hydraulic fluid that has been forcing the ram 16 into thetop-of-its-stroke position shown in FIG. 3, causing the entire reversalof the flows of hydraulic fluid previously described so that thehydraulic fluid flows along the lines of the reverse directiondirectional arrows 72. As hydraulic fluid flows through the opendirectional valve 68, some of it flows through the pressure relief line56 to the top surface 64 of the shuttle member 30 along the pressurerelief directional flow arrows 74, i.e., toward the left-hand side ofFIG. 4 as shown. The shuttle member 30 thereby provides a movable sealon the vessels that contain the hydraulic fluid, which becomes importantin the downstroke of the ram 16. Other portions of the hydraulic fluidflow toward the right-hand side of FIG. 4 as shown, through the pressurerelief line 56 to the pressure relief tank 58 as shown by the pressurerelief tank flow directional arrows 76, assuring that the high pressurepump 54 cannot contribute to any hydraulic pressure in the upper pistonchamber 50. Combining the stopping of applying more hydraulic fluidpressure into the upper piston chamber 50 and relieving the existingpressure via the pressure relief line 56 removes the forces that keepthe ram 16 suspended above the pile 14, causing the ram 16 to fall.

Referring to FIG. 5, the ram 16 is essentially falling in free-fall andis accelerating at approximately the rate of gravitational acceleration,aided by the additional force developed by the compressed gas in thevariable volume cavity 41 acting on the lower surface of the piston 26.As the ram 16 falls, the volume of the lower piston chamber 29increases, causing the gas pressure within the sealed system of thelower piston chamber 29 and the interior of the hollow piston rod 40 todecrease. The decreased gas pressure is eventually insufficient tosupport the shuttle member 30 against the upper stop member 32, as shownin FIG. 4, so the shuttle member 30 falls within the hollow piston rod40, which creates a certain amount of downward force, that is, theproduction of a lower pressure in the variable volume cavity 41 as thevariable volume 41 expands due to the falling of the ram 16. At the sametime, the hydraulic fluid is flowing along the direction of thedirectional arrows 74, creating downward force on the shuttle member 30,which in turn aids in drawing out hydraulic fluid from the upper pistonchamber 50 faster than would occur if the only pressure relief were toprovide a zero pressure pressure relief line. Because the gas in thelower piston chamber 29 and hollow piston rod 40 is sealed and thepressure on it varies only due to movement of the ram 16 relative to thepiston 26 and the up or down position of the shuttle member 30 insidethe hollow piston rod 40, the shuttle member 30 reciprocates up and downas the lower piston chamber increases or decreases. Since the gas iscompressible, the movement of the shuttle member 30 acts like a spring,drawing further pressure off of the hydraulic fluid during the fallingram 16 step of the cycle and allowing the ram 16 to fall more nearly atthe speed of gravity, since less of the gravitational drop energy isused to extract hydraulic fluid from the upper piston chamber 50 thanwould otherwise be the case. The movement of the shuttle member 30 andram 16, which vary the volume of the sealed chamber 29 provides a springaction in the form of a downward force to accelerate the emptying ofhydraulic fluid from the upper piston chamber 50. The magnitude of thedownward force of the compressing gas on the ram 16 in the sealedchamber 29 can be controlled or modified by setting the pre-load orstatic equilibrium pressure int the sealed chamber 29 (and the alsosealed volume of the interior of the hollow piston rod cavity 28 belowthe shuttle member 30, which varies throughout an up and down cycle ofthe ram 16, as described above) at the beginning of the lifting step ofthe cycle, as shown, for example, in FIG. 2.

Referring to FIG. 6, in the time between the positions of the partsshown in FIGS. 5, 6, the ram 16 has continued its fall until, as shownin FIG. 6, the shuttle member 30 being drawn downward to its lowestpoint where it contacts the lower stop member 36, which also marks thelargest volume of the lower piston chamber 29 and the lowest resultinggas pressure within the lower piston chamber, simultaneously exertingthe strongest sucking force on the hydraulic fluid that now fills thevolume 40 of the hollow piston rod 28 as the shuttle member 30 fallstoward the lower stop member 36. At the moment that the shuttle member30 strikes the lower stop member 36 and the ram 16 strikes the pile 14,the hammer 10 is again at rest and equilibrium and ready for the startof the next stroke, which is initiated by closing the directional valve68 and once again forcing hydraulic fluid into the upper piston chamber50 to force the ram 16 to rise.

Referring to FIGS. 8-13 and 7, an alternative embodiment of the hammer10 is shown. This embodiment is a low headroom hammer. The structure ofthis embodiment is identical to the structure of the embodiment of FIG.1-7 except that the shuttle member 30 and the related stops 32, 36, 38are omitted. This change leads to a single fluid hydraulic hammer, whichis again any suitable substantially incompressible fluid, such as oil,hydraulic fluid, water or the like. The steps involved in the cycling ofthe embodiment of FIGS. 8-13 are identical to those described above indetail relative to the embodiment of FIGS. 1-7, but the fluid flows aredifferent due to the use of a single fluid and these are describedimmediately below. This embodiment requires a higher pressure hydraulicsystem than the embodiment shown in FIGS. 1-6 to achieve the same cycletimes because a greater weight or mass of hydraulic fluid must be moved.

As shown in FIG. 8, the hammer 10 is at rest, the directional valve 68is open and there is no pressure or fluid flow inside the hammer 10 orthe high-pressure hydraulic fluid line 52 leading to it or the pressurerelief line 56 leading away from it.

Referring to FIG. 9, the directional valve 68 is closed, causing theflow from the high-pressure hydraulic fluid pump 54 to flow through theline along the directional arrows 70 and into and down the tube 42 andinto the upper piston chamber 50, thereby increasing the volume of theupper piston chamber 50 as it fills with fluid and thereby pulling theram or actuator 16 up, beginning the lift portion of the cycle. At thesame time, the hydraulic fluid inside the lower piston chamber 29beneath the piston 26 is forced upwardly through the hollow piston rodcavity 28 along the path of the directional arrows 90 and through thepressure relief line 56 and to the pressure relief tank 58. Theadvantage of this embodiment over the embodiment of FIGS. 1-6 is that inthe present embodiment, the elimination of the shuttle member reducesthe complexity of the hammer 10 and the necessity of providing separategas and liquid fluid compartments and the necessity of using asubstantially inert gas to prevent possible explosions. The advantage ofthe embodiment of FIGS. 1-6 to this embodiment is that the embodiment ofFIGS. 1-6 can be expected to have faster cycle times and achieve closerto free-fall operation because in this embodiment of FIGS. 1-7, asmaller volume of hydraulic fluid is used and there is the previouslydescribed air-spring effect that encourages the downward movement of thehammer 10 when it is dropped.

Referring to FIG. 11, at the predetermined desired height of the ram 16,the directional valve 68 is opened, relieving all the pressure on insidethe hammer 10, causing the hydraulic fluid to flow upward through thetube 42 along the lines of the directional arrows 92 and into thehigh-pressure hydraulic fluid line 52. At the same time, pressurizedhydraulic fluid from the high-pressure hydraulic pump 54 flows into thehigh-pressure hydraulic fluid line 52 along the path indicated by thedirectional arrows 94. Flows along the directional arrows 92 and 94merge as they flow through the open directional valve 68 indicated bythe merge arrow 96, causing the flow of hydraulic fluid through thepressure relief line 56 along the direction of the arrows 98 and therebydownwardly through the hollow piston rod cavity 28 and into the lowerpiston chamber 29, causing the volume of the lower piston chamber 29 toincrease. Relieving the hydraulic fluid pressure on the top of thepiston 26 in the upper piston chamber 50 allows gravity to cause the ram10 to fall, with the pressurized hydraulic fluid flowing into the lowerpiston chamber 29 accelerates the fall, helping overcome frictionallosses and so forth.

FIG. 12 shows the hammer 10 in the falling portion of the cycle fartherdown toward the pile 14, with the fluid flows shown in FIG. 11continuing.

FIG. 13 shows the hammer 10 returned to its equilibrium position atimpact, that is with no hydraulic pressure inside the hammer 10 atimpact.

Referring to FIG. 14, another embodiment of the hammer is shown in a theform of a modification that can be used with the embodiment of FIGS. 1-6or the embodiment of FIGS. 8-14. As shown in FIG. 14, a cylinder havinga closed lower end is attached to the lower surface of a piston, i.e.,forming a receptacle 78, which resembles a bucket, suspended beneath thepiston 26 and reciprocating within a well 82 below the otherwise normalfloor of the piston cylinder to reduce the volume of fluid that must beremoved from the cylinder space below the piston, that is in the lowerpiston chamber 29, showing the hammer 10 at the completion of a downwardstrike on a pile or the like in equilibrium, at rest and ready to beginthe lifting stroke of its cycle. The receptacle 78 is attached to thelower surface of the piston 26 by welding 80, but may be connected byany convenient means, such as threaded connection, brazing, bolting andthe like. A plurality of perforations 81 are formed into an upper end ofthe receptacle 78 to allow the flow of hydraulic fluid from inside thereceptacle 78 to outside the receptacle 78 and into the annular volumeoutside the receptacle 78, although there will be little flow, seebelow. Cut into the bottom wall 25 of the piston cylinder and into theram 10 is a well 82, directly beneath the receptacle 78. Suitable sealsin the bottom wall 25 prevent leakage of fluids around the perimeter ofthe receptacle 78, which reciprocates in tandem with the piston 26. Thisis not a low headroom embodiment, since the overall length must begreater in order to accommodate the well 82. The advantage of thisembodiment is that the hydraulic fluid that is captured in thereceptacle 78, which remains substantially static at all times, need notbe pumped out of the lower piston chamber 29 during any portion of thecycle of lifting and falling, reducing the amount of hydraulic fluidthat must be pumped, thereby reducing cycle times for a given capacityhydraulic pump 54. The disadvantages of this embodiment are that it ismore complicated to build and maintain and likely cannot be made a lowheadroom hammer of substantial impact power.

Still referring to FIG. 14, as shown in FIGS. 14-19, this embodiment isshown without the shuttle member 30, upper stop member 32 and lower stopmember 36 as previously disclosed in relation to FIGS. 8-13, but thismodification can also be used with the embodiment of FIGS. 1-6. Ineither case, the fluids and the fluid flows are the same as describedabove in connection with their respective embodiments. When thismodification is used with the embodiment of FIGS. 1-6, the shuttlemember 30 and its upper stop member 32 and lower stop member 36 areincluded. When the embodiment of FIG. 14 is used with the embodiment ofFIGS. 8-13, the shuttle member 30 and its upper stop member 32 and lowerstop member 36 are omitted and a single working fluid is used and thefluid flows are those described above in connection with FIGS. 8-13.

Referring to FIG. 15, at the beginning of the lifting of the ram 16, thefluid flows are the same as those shown in FIG. 9 and as described inthe description of FIG. 9.

Referring to FIG. 16, the lifting of the ram is continued and the fluidflows are those shown in FIG. 10 and as described in connection withFIG. 10.

Referring to FIG. 17, the ram 16 has reached its predetermined desiredheight and the directional valve 68 is opened, changing the fluid flowsto those shown in FIG. 11 and described in connection with FIG. 11.

Referring to FIG. 18, the fluid flows shown in FIG. 17 continue,allowing the ram 16 to continue its descent.

Referring to FIG. 19, the directional valve 68 remains open, and the ram16 has continued to fall until it strikes the pile 14 and is ready forthe next cycle, initiated by closing the directional valve 68.

Referring to FIG. 20, in a modification of the embodiment of FIG. 19, alid 84 is sealed across the top of the receptacle 78 duringmanufacturing, sealing a substantially inert gas such as Nitrogeninside, thereby reducing the weight of the receptacle 78 and contents,thereby reducing the reciprocating weight of the piston 26 and thereceptacle 78 and its contents.

Referring to FIG. 21, there is shown an alternative embodiment of thehammer 10 in which the sleeve 17 and connected bottom wall 25 assemblyis suspended within the cavity 19 in the ram 16 with an annular space100 between these two members, including between the bottom wall 25 ofthe sleeve 17 and bottom wall 25 assembly and a bottom wall 102 of thecavity 19, which is partially filled with oil or other fluid. The oilfills the annular space 100 nearly to the lower surface of the cylinderhead 48, but a significant gas gap is preserved so that the oil canslosh around. This arrangement makes the piston 26 and piston cylinder24 self-aligning with the ram 16, that is, in the case that, forwhatever reason, the ram 16 and piston 26 and piston cylinder 24 areurged to move along somewhat different lines, the annular space 100 andoil 88 allow for this state without damaging either the ram 16 or thepiston 26 and piston cylinder 24 assembly and further, urges thesemembers back into vertical alignment.

Referring to FIG. 22, the modification of FIG. 14, that is, includingthe receptacle 78 and the well 82, is shown in use with the embodimentof FIGS. 1-6, that is the embodiment utilizing the shuttle member 30 andits upper and lower stop members 34, 36. The stages of the reciprocatingcycle and the fluids flows are therefore identical to those shown inFIGS. 1-6 and as described above in connection with FIGS. 1-6.

The hammer 10 has shorter cycle times than related hammers of similarstriking capacity and uses less hydraulic fluid and a smaller capacityhydraulic pump. The embodiment utilizing the shuttle member 30 uses lessenergy than a now standard hydraulic hammer due to the use of the gaschamber actuating the moveable shuttle member, providing a spring effectto more quickly and efficiently empty the upper piston chamber ofhydraulic fluid for the nearly free-fall gravity operated downstroke.The embodiment utilizing the receptacle reciprocating in the well alsouses less energy than a now standard hydraulic hammer because the volumeand weight of hydraulic fluid that must be exhausted from the chamberbeneath the piston is reduced. The hammer 10, in, for example, theembodiment shown in FIGS. 1-6, is also a very low headroom hammer due tothe advancement of forming the piston cylinder inside the ram itself.

While the present invention has been described in accordance with thepreferred embodiments thereof, the description is for illustration onlyand should not be construed as limiting the scope of the invention.Various changes and modifications may be made by those skilled in theart without departing from the spirit and scope of the invention asdefined by the following claims.

We claim:
 1. A hydraulic hammer comprising a ram and a piston cylinderformed inside said ram, a piston seated in said cylinder, with saidpiston fixed to a lower end of a connecting rod with an upper end ofsaid connecting rod fixed to a support member above said ram andhydraulic means operatively connected to said ram for moving said rambetween a first position and a second position.
 2. A hydraulic hammer inaccordance with claim 1 wherein said hydraulic means further comprises asource of pressurized hydraulic fluid operatively connected to an upperpiston chamber created by a piston inserted into said cylinder and acylinder head above said piston for creating hydraulic pressure insidesaid upper piston chamber and wherein said piston is fixed to a lowerend of a piston rod and means for selectively relieving hydraulic fluidpressure inside said upper piston chamber.
 3. A hydraulic hammer inaccordance with claim 1 wherein said piston rod is hollow and furthercomprising a shuttle member seated within said hollow piston rod, saidhollow piston rod having an upper end fixed to a supporting member andwherein said shuttle member is free to reciprocate within said hollowpiston rod.
 4. A hydraulic hammer in accordance with claim 3 whereinsaid pressure relieving means further comprises a valve in a pressurizedhydraulic fluid source that can be opened to allow pressurized hydraulicfluid to flow into a pressure relief line.
 5. A hydraulic hammer inaccordance with claim 4 wherein said pressure relief line furthercomprises a passageway to an upper surface of said shuttle member insidesaid hollow piston rod.
 6. A hydraulic hammer in accordance with claim 3wherein said source of pressurized hydraulic fluid operatively connectedto said upper piston chamber further comprises a hydraulic fluid conduittube larger in diameter than said hollow piston rod and concentric withsaid hollow piston rod.
 7. A hydraulic hammer in accordance with claim 5further comprising a lower piston chamber and a cavity of said hollowpiston rod below a lower surface of said shuttle member that furthercomprises a sealed cavity that is filled with a substantially inert gasunder pressure.
 8. A hydraulic hammer in accordance with claim 7 whereinthe volume of said lower piston chamber and said cavity of said hollowpiston rod below a lower surface of said shuttle member form a variablevolume cavity that varies in volume as said ram moves between said firstand second positions.
 9. A hydraulic hammer in accordance with claim 2further comprising upper and lower stop members seated inside saidhollow piston rod for constraining the reciprocal movements of saidshuttle member.
 10. A hydraulic hammer in accordance with claim 2wherein said cylinder further comprises a sleeve inserted into saidcylinder.
 11. A hydraulic hammer comprising; a. a ram; b. a cylinderformed inside said ram and sealed at its lower end and sealed at itsupper end by a cylinder head; c. a piston seated in said cylinder anddividing said cylinder into an upper piston chamber and a lower pistonchamber; d. a hollow piston rod having an upper end fixed to asupporting member and a lower end fixed to said piston.
 12. A hydraulichammer in accordance with claim 11 further comprising means forsupplying hydraulic fluid under pressure to said upper piston chamber.13. A hydraulic hammer in accordance with claim 11 further comprisingmeans for releasing hydraulic pressure from said upper piston chamber.14. A hydraulic hammer in accordance with claim 13 further comprisingmeans for applying a force to a lower surface of said piston foraccelerating the relief of pressure from the hydraulic fluid in saidupper piston chamber and thereby accelerating the falling of said ram.15. A hydraulic hammer in accordance with claim 14 wherein said forceapplying means further comprises a shuttle member seated inside saidhollow piston rod and free to reciprocate between upper and lower stopmembers.
 16. A hydraulic hammer in accordance with claim 15 furthercomprising a sealed chamber filled with gas under pressure, with saidsealed chamber comprising said lower piston chamber and a cavity in saidhollow piston rod up to a lower surface of said shuttle member, withsaid lower piston chamber and said cavity in said hollow piston rodbeing in fluid communication with each other.
 17. A hydraulic hammer inaccordance with claim 16 wherein said gas under pressure when acted uponby a varying volume of said variable volume cavity during movements ofsaid ram and said shuttle member provides a spring action expansionforce to said lower surface of said piston to accelerate the emptying ofhydraulic fluid from said upper piston chamber.
 18. A hydraulic hammercomprising; a. a ram; b. a cylinder formed inside said ram and sealed atits lower end and at its upper end; c. a piston seated in said cylinderand dividing said cylinder into an upper piston chamber and a lowerpiston chamber; d. a hollow piston rod having an upper end fixed to asupporting member and a lower end fixed to said piston; e. means forapplying hydraulic fluid pressure to said upper piston chamber forraising said ram and means for relieving said hydraulic fluid pressurein said upper piston cylinder for allowing said ram to fall and meansfor introducing hydraulic fluid into a lower piston chamber as said ramfalls for accelerating the falling of said ram.
 19. A hydraulic hammerin accordance with claim 18 further comprising a receptacle attached toa lower surface of said piston and depending therefrom and a wellbeneath said receptacle formed in said ram whereby the volume ofhydraulic fluid to be pumped is reduced.
 20. A hydraulic hammer inaccordance with claim 19 further comprising means for supplyinghydraulic fluid under pressure to said upper piston cylinder and meansfor relieving the pressure on the hydraulic fluid and for emptying thehydraulic fluid from said upper piston chamber and means for applying adownward acceleration force on said ram, said accelerating means furthercomprising means for controlling the magnitude of said downwardacceleration force.